1. Field of the Invention
This invention relates to an image memory device, and more particularly to an image memory device wherein interpolation data are successively obtained from a frame memory in order to process a moving picture image.
2. Description of the Related Art
A system wherein digital image data are read out from a frame memory while interpolation calculation is performed is conventionally known and disclosed, for example, in Japanese Patent Laid-Open Application No. Showa 60-21677. In the prior art system, a frame memory for storing image data includes an odd-numbered field memory for storing image data of odd-numbered lines and an even-numbered field memory for storing image data of even-numbered lines, and data are read out from the odd- and even-numbered field memories in such a manner that they are partially overlapped with each other in a horizontal direction and a vertical direction to allow data necessary for interpolation for neighboring points to be read out from the frame memory. Consequently, arbitrary coordinate data which are not stored in the frame memory can be obtained by interpolation processing, and accordingly, a conversion image of a high quality can be obtained.
The prior art system employs such a complicated reading out method that data are successively read out alternately from the odd- and even-numbered field memories of the frame memory for successive lines and image data are partially overlapped with each other for both of a horizontal direction and a vertical direction in order to perform interpolation calculation. Consequently, even upon, for example, simple interpolation calculation for four points, data must be read separately by second times for each line, and besides, reading out of data for different lines must be performed sequentially. Accordingly, it is impossible to read out data necessary for interpolation at a time and a long processing time for interpolation is required. Further, a timing control circuit for such complicated reading out operation as described above is required.